South Park co-creator is a Libertarian, Libertarian Party News, May 2001
"... in an April 4 Los Angeles Times article, [Parker] described himself as a 'registered Libertarian.' ... In November 2000, the National Review complimented South Park for its 'extremely amusing libertarian-minded political commentary.'"

South Park Libertarians: Trey Parker and Matt Stone on liberals, conservatives, censorship, and religion., by Nick Gillespie, Reason, Dec 2006
Related Topics: South Park
Transcript of conversation with Trey Parker and Matt Stone, at Reason's Aug 2006 conference in Amsterdam
"Reason: Each of you at various points have called yourself libertarian. Is that an apt description? Parker: People started throwing that word around to describe us right around the second or third season. They would sit us down and go, 'So are you libertarian?' And I would always say, 'I don't know, am I? You've seen my stuff.' I still don't really know the answer to that question. I think I am, though."

The Invisible Gnomes and the Invisible Hand: South Park and Libertarian Philosophy, by Paul Cantor, 4 Dec 2006
Related Topics: South Park, Capitalism, Libertarianism
Includes detailed review and discussion of season 2 "Gnomes" episode
"The genius of Parker and Stone was to see that in our day a new frontier of comic transgression has opened up because of the phenomenon known as political correctness. ... Like Adam Smith, Parker and Stone are deeply suspicious of people who speak about the public good and condemn the private pursuit of profit."

Films

South Park - Bigger, Longer & Uncut
by Trey Parker (Director, Writer, Voice of Stan Marsh, Eric Cartman, etc.), Matt Stone (Writer, Voice of Kyle Broslofski, Kenny McCormick, etc.), 1999